Thousands of people will be heading overseas on holiday this Easter to take advantage of the long weekend, but delaying buying foreign currency until you reach the airport could leave a nasty hole in your pocket.

Due to the plummeting value of the pound, many people will find that their holiday spending money has already been greatly curtailed, so getting a good deal on foreign currency is more important than ever before.

At the beginning of this week £1 was worth about €1.07 - meaning that after commission and handling fees, holidaymakers at some airports were getting less than a euro for every pound changed. At its highest in the year 2000, the pound was worth more than €1.70.

Brits buying their holiday spending money from Heathrow, however, will get even less bang for their buck - just €0.9853 to the pound.

"Airport travel money bureaux have long taken advantage of travellers who leave buying their holiday cash until they reach the airport by offering far worse rates than outside the terminal," said Stephen Heath, chief executive of fairfx.com. "And now Heathrow has become the biggest airport out of many to offer below parity."

The best exchange rates can usually be found online, although rates vary widely depending on which provider you use. For example, if you ordered €500 from Travel Money Services via its website travelmoneyservices.co.uk last Monday, this would cost £473.40 at an exchange rate of €1.056 to the pound.

Thomas Global Exchange also offers competitive rates, offering €500 for £476.19. You can collect the money from its two London branches, or have it delivered for £5.

The same amount of euros bought online from fx4you.com, which is American Express's internet service, would set you back nearly £20 more than if you had bought them through Travel Money Services. The cost would be £491.50, based on an exchange rate of €1.017. Travelex offered a rate of €1.040, giving €500 at a cost of £481. This is the online rate; currency bought at Travelex branches in airports and terminals will have less competitive rates. Our table shows how these and other rates compare.

Remember that exchange rates change daily, so these rates may not be the same as the ones you are offered when you order your travel money. It's always worth comparing at least four or five providers to make sure you're getting a good deal.

Many people prefer to just take plastic when they travel abroad, but if you don't take the right card you could also find yourself stung by charges. Most banks charge holidaymakers using debit or credit cards to buy goods or services overseas a steep 2.75% foreign usage conversion fee. So, if you spent £150 on a dinner for the family in France, you could expect to be charged a further £4.13 on top of this, or 2.75% of the cost.

Many debit cards also charge an additional fee, often 1.5%, each time you make a cash withdrawal, and will charge up to £1.50 for every purchase. Credit cards usually charge even steeper fees, of up to 3% for cash withdrawals, on top of the usual 2.75% conversion fee.

Andrew Hagger of moneynet.co.uk said: "It is better that consumers are aware of these charges before they jet off, rather than get a nasty shock after they arrive home. At least

if you understand the overseas charges, you could adjust your spending accordingly. You don't want to be making cash withdrawals or purchases of £10 or £20 if you're going to

be hit with charges of £1.50 plus each time. These charges don't sound much in isolation. However, if you look at a scenario where a family is on holiday for two weeks and make five debit-card cash withdrawals of £100 currency equivalent and eight debit card purchases of £50 currency equivalent, they could be faced with a bill of almost £45."

If you are taking a debit card abroad, Nationwide's Flexaccount Visa doesn't have any foreign usage loading fees. There is no fee for cash withdrawals abroad either but, be warned - the Nationwide is introducing a 0.84% fee on credit card purchases made worldwide, excluding Europe, from 6 May. The fee will rise to 1% on 1 July. The same 0.84% fee will apply to worldwide debit card transactions, excluding Europe, from 1 June, again rising to 1% from July.

If you want to take a credit card, the Post Office still doesn't charge any foreign exchange loading fees, although you will have to pay a 2.5% charge for every cash machine withdrawal. The minimum charge is £3.

Nationwide's credit card - until May only - doesn't have any foreign loading fees, although again there is a 2.5% charge for withdrawals.